Steering gear



Dec. 24, 1940- F IESTCQTT ETAL I STEERING GEAR Filed March 25, 1959 6Sheets-Sheet 1 In veniors ymnk 952520051? & fairs Wow/oval A ttorneysDec. 24, 1940. I F. WESTCOTT ETAL 2,226,038

STEERING GEAR Filed March 25, 1939 6 Sheets-Sheet 2 In ventors 77 m5202522012 A? 2 0/221 ZZMZu aacl Dec. 24, 1940. F. wEsTcoTT ETAL2,226,038

STEERING. GEAR Filed March 25, 1939 e Shets-Sheet a Fig. 4..

In ven tors 7712221: fllfsszcott & johzz Ho {wood Dec. 24, 1940. F.WESTCOTT EIAL 2,226,038

STEERING GEAR Filed March 25, 1959 s Sheets-Sheet 4 r v, Attorneys Dec.24, 1940. F. wEsTco'TT ET A1.

STEERING GEAR Fiied March 25, 1939 s Sheets-Sheet s- Fig. 6.

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Dec. 24, 1940. F. WESTCOTT ET AL STEERING GEAR Filed March 25, 1939 6Sheets-Sheet 6 Inventor Wmzzk Wesicott 4% john bfio iu o 0d y 9/ Atlnrneys Patented Dec. 24, 1940 UNITED STATES PATENT OFFICE STEERINGGEAR Delaware Application March 25, 1939, Serial No. 264,070 In GreatBritain March 29, 1938 Claims. (Cl. 74-499) This invention relates tosteering gears for motor vehicles and particularly to the adjustment oftoothed gearing therein.

The object of the invention which can be ap- 5 plied to various forms ofsteering gear, is to simplify the adjustment of such toothed gearing forthe elimination of backlash.

The adjustment is effected by relative movement between theinter-engaging tooth or like members in the direction of an axis, andthis is made possible by making the teeth on one or both of the twointer-meshing members of tapered thickness. The teeth may be cut by anyof the usual generating methods.

In the embodiments of the invention hereinafter particularly describedvarious forms of inter-engaging members are used: the rocker shaftcarries a toothed member which may be. a gear sector; and the steeringshaft carries av grooved member which may be a; rack or a worm. In allcases, adjustment is effected by a relative movement between the twomembers, preferably an axial movement of the rocker shaft.

The scope of the invention is indicated by the appended claims, and itsnature will be better understood from the following description taken inconjunction with the accompanying drawings, in which- Figure 1 is adiagram illustrating the preferred method of forming a tapered toothgear for use in a steering gear;

Figures 2 and 3 are respectively end and side views of a tapered toothgear, formed according to the method illustrated by Figure 1, meshingwith a rack;

Figures 4 and 5 are respectively transverse and longitudinal sectionalviews of one form of steering gear according to the invention, the twotoothed members engaging in the manner shown in Figures 2 and 3;

Figures 6 and 7 are similar views of another form of steering gear; and

Figures 8 and 9 are similar views of a still further form of steeringgear.

In the various figures, like reference characters indicate like parts.

The simplest and preferred method of forming the tapered tooth gear isby generating with a shaping cutter as used for example in a Fellowsmachine. A rotary or rack cutter may be used; and. the former is shownin the diagram of Figure 1. The machine is of standard form but with thedifference that the cutter a moves at an angle to the axis of the shaft12 carrying the sector blank c. It is not considered necessary to showthe various internal parts of the machine for ensuring the usualrelative rolling and like movements between the cutter and the work. Itwill be noticed that the outer surface of the sector 6 is conical, thegenerating line being parallel to the direction of the stroke of thecutter a.

If desired the gear may be cut by a hob and the simplest arrangement, toproduce the required tapered tooth, is to give the hob a stroke 10 at anangle to the work axis as above described. This angular movement can beobtained, alternatively, by producing a relative infeed of the cuttertowards the work during the working stroke. 1

In making the teeth by another method one side of each tooth is firstcut at an angle as in cutting an ordinary helical pinion and then theopposite side of each tooth is cut but with the angle reversed. In thisway each tooth will be 20 tapered, from one side of the gear to theother. The cutting tool in such a case must be narrow enough to passthrough the narrowest part of the space between successive pairs ofteeth. A rack can be cut in a similar manner, by successive cuts 25 onopposite sides of each tooth, at reversed angles.

In Figures 2 and 3 are shown on an enlarged scale the teeth d of asector 0, out according to the method illustrated in Figure 1, meshingwith teeth e of a rack j. The teeth d which are true 30 involutes offthe same base cylinder cut to pressure angle a, mesh with thestraight-cut teeth e of rack} which as shown in Figure 3 is setobliquely. The teeth d increase in thickness from r the smaller diameterto the greater diameter; that is from the right to the left of Figure 2,and from the dotted shape tothe full line shape of Figure 3. Linecontact between the sector teeth d and rack teeth e is maintained acrossthe whole width of the gear in all positions of engagement, 40 this linebeing a skew line relative to the sector axis. The lengths of therespective lines of action at the thick and thin ends of the teeth d areshown in Figure 3 by :3 and 7 respectively. As 45 shown in Figure 2, theaddendum of a tooth d increases and the dedendum decreases, relative tothe virtual side 11-1) of the pitch cylinder, from the right-hand sideto the left-hand side; whilst the root diameter and outside diameterincrease 60 from the right-hand side to the left-hand side, the toothdepth being constant. Although the rack teeth e are parallel cut. yetdue to their oblique disposition their effective addendum and dedendumvary inversely to those of the teeth d, across the tooth width. Thisallows for any required axial adjustment of the sector c and rack I.

How such toothed members are used in steering gears on motor vehicleswill now be described with reference to Figures 4 to 9. In each form ofgear, adjustment can easily be made by movement of rocker shaft inwardlytowards the steering shaft.

In the steering gear shown in Figures 4 and 5 a worm a mounted on thesteering shaft h carries a series of balls i held partly in the threadof the worm and partly within an internal thread in a cage member :i.Rotation.of the shaft h and worm 0 causes the balls i to circulatearound the threads, and the cage member is carried axially along theworm. The balls are returned from one end of the cage member 1 to theother, externally by means of a conduit is on the cage member. On thecage member is cut an ordinary straight rack f as shown in Figures 2 and3. Meshing with this rack is the toothed sector c formed as describedabove. The sector is mounted on the rocker shaft b which is movableaxially in its bearings by means of an external screw adjusting membern. Thus, any backlash in the steering gear can be taken up by rotatingthe screw member 11 and moving the rocker shaft b axially to the right(Figure 4) so as to slide the tapered teeth d on the sector 0 into theteeth e of the rack f.

The rack j and cage member :I are tilted obliquely about the axis of theworm 0. as clearly seen in Figure 4. Thus while the plane of thesurfaces of the tips of the rack teeth is at an angle to the axis of therocker shaft 17, it is itself normal to the inclined median longitudinalplane of the cage.

In Figures 6 and 7 a simplified form of rack and sector steering gear isshown. In this construction the worm g carries a nut 9 directly by meansof the usual inter-engaging threads, without the interposition of ballbearings. The nut carries the rack 1 which engages the sector 0 aspreviously described. The rack is cut obliquely instead of being setobliquely. The sector c and the rocker shaft b can be moved axially tothe right (Figure 8) to take up backlash, in the manner previouslydescribed.

In Figures 8 and 9 there is shown a simple hour-glass-worm, and sectorconstruction. On the steering shaft h is mounted a worm q of the usualhour-glass shape, and meshing with it, is the sector 0 having taperedteeth d and mounted on the rocker shaft b. As will be clear from Figure8 the sector c can be moved by screw member 11, to the right, closer tothe axis of the worm q, and thus take up backlash.

It will be seen from the above that steering gears embodying taperedtoothed members, according to the above invention, can take variousforms and the above described embodiments are to be taken simply asillustrative in that respect.

We claim:

1. A steering gear for use on motor vehicles,

comprising a steering shaft carrying a threaded member, a toothed memberon said threaded member and movable axially therealong upon rotationthereof, a rocker shaft carrying a second toothed member meshing withthe first toothed 5 member, the teeth of the respective members varyinginversely in width and inversely with increasing and decreasing addendaand dedenda, and means for axially adjusting said rocker shaft.

2. A steering gear for use on motor vehicles, 10 comprising a steeringshaft carrying a threaded member, a correspondingly internally threadedrack member on said threaded member and movable axially therealong uponrotation thereof, a rocker shaft carrying a toothed member meshing 15with said rack member, the teeth of the respective toothed membersvarying inversely in width and inversely with increasing and decreasingaddenda and dedenda from one side' to the other, and means for axiallyadjusting said rocker shaft. 20

.8. A steering gear for use on motor vehicles, comprising a steeringshaft carrying a threaded member, an internally threaded cage membermounted thereon, a series of balls movable along the mutually opposedthreads of said members, a conduit on said cage'member for transferringthe balls from one end thereof to the other, a rack on said cage member,a rocker shaft carrying a toothed member in operative drivingrelationship with said rack, the teeth on said toothed member being ofconstant height of increasing addendum and decreasing dedendum and ofincreasing width from one side to the other, and means for axiallyadjusting said rocker shaft.

4. A steering gear for use on motor vehicles, comprising a steeringshaft carrying a threaded member, a correspondingly internally threadedrack member mounted thereon, a rocker shaft carrying a toothed membermeshing with said rack, the teeth on said toothed member being 40 ofconstant height of increasing addendum and decreasing dedendum, and ofincreasing width from one side to the other, and the longitudinal medianplane of said rack member being oblique to the rocker shaft axis, andmeans for axially 45 adjusting said rocker shaft.

5. A steering gear for use on motor vehicles, comprising a steeringshaft carrying a threaded member, an internally threaded cage member.mounted thereon, a series of balls movable along 50 the mutuallyopposed threads of said members, a conduit on said cage member fortransferring the balls from one end thereof to the other, a rack on saidcage member, a rocker shaft carrying a toothed member meshing with saidrack member, the teeth of the respective toothed members varyinginversely in width and inversely with increasing and decreasing addendaand dedenda from one side to the other and the iongitudinal median planeof said rack member being oblique to the rocker shaft axis, and meansfor axially adjusting said rocker shaft.

FRANK WESTCOTT. JOHN NORWOOD. 65

